The Mars Atmosphere and Volatile Evolution, or MAVEN, mission is being sent to the red planet to answer a fundamental question: Why did Mars dry up and cool off?

The MAVEN spacecraft arrived at the Kennedy Space Center on Aug. 2 on a U.S. Air Force C-17 transport plane. MAVEN was built by Lockheed Martin in Denver, then moved to Florida for final launch preparations.

"We're in good shape," said David Mitchell, MAVEN project manager at NASA's Goddard Space Flight Center in Maryland. "I don't want to claim success until we're actually there, [but] I'll say right now we're on the plan and on the budget. It's a tremendous thing the team has accomplished."

Its launch is scheduled aboard a United Launch Alliance Atlas 5 rocket from Cape Canaveral on Nov. 18. The mission has 20 days to depart Earth, or else stay grounded for 26 months to wait for the planets to properly align again to make the journey possible.

"When you have a planetary launch period of 20 days, and then you have to stand down for 26 months, there's a real sense of urgency in decision-making and trades to keep moving forward," Mitchell said.

MAVEN is NASA's 10th Mars mission to launch since 1996. Eight of those reached their destinations, either Mars orbit or the red planet's surface.

The armada of probes dispatched to Mars in the last 15 years have answered key questions about Mars, its evolution, habitability and geology. But while scientists know more about the Martian environment of today and yesteryear, Bruce Jakosky, MAVEN's principal investigator, said little is known about how Mars transitioned from a warmer, wetter world into the barren planet of today.

"We're trying to understand why the climate changed on Mars - why Mars appears to have gone from an environment that was habitable, to microorganisms at least, to one that is the cold, dry, uninhabitable environment we see today," said Jakosky, a scientist from the University of Colorado at Boulder's Laboratory for Atmospheric and Space Physics. "By looking at the nature of the upper atmosphere today, we learn about the processes that control the atmopshere, and we're going to have a good understanding of what the history of the atmosphere has been."

Mitchell and Jakosky said teams are focused on keeping MAVEN on track for its Nov. 18 launch date.

An artist's concept of MAVEN orbiting Mars. Credit: NASA

"To see it safely here in Florida, the last destination before it heads to Mars, is incredible," Mitchell said. "It's been a lot of years working together, and it's been a great team effort. They've landed it right on schedule, and we're still tracking to the original launch date we had planned when our proposal was selected five years ago."

MAVEN was selected by NASA in 2008 after a competition, beating out another orbiter that would have measured biogenic constituents such as methane in the atmosphere.

Officials say MAVEN's total cost is $671 million. That figure includes the costs of constructing the spacecraft, the Atlas 5 launcher, and a year of operations at the red planet.

Lockheed Martin, which has a history of building interplanetary probes for NASA, used work on previous missions to MAVEN's benefit, said Guy Beutelschies, the company's MAVEN program manager.

Beutelschies said designers based MAVEN's spacecraft bus, propulsion module and communications systems on the Mars Reconnaissance Orbiter, which launched to the red planet in 2005. And engineers recycled much of the software and avionics used on NASA's Jupiter-bound Juno mission for MAVEN.

"The structure of MAVEN is almost identical to MRO," Beutelschies said, adding MAVEN is a bit smaller but has a larger fuel tank.

Lockheed Martin also altered MAVEN's solar panels, which extend 37.5 tip-to-tip feet when unfurled, to be canted at an angle on each end. Beutelschies said the design makes the spacecraft more stable when it dips into the Martian atmosphere, which MAVEN will do at least five times to get a taste of what is going on at lower altitudes.

Technicians began assembling MAVEN in Denver last summer, then Lockheed Martin put the spacecraft through a series of extensive of tests to ensure the probe will survive the vibrations and acoustic noise of launch and the extreme temperatures and vacuum of space.

MAVEN came through the tests unscathed, and engineers put the spacecraft inside an 18-foot-tall canister for shipment to Cape Canaveral. Workers opened up the box inside a clean room at KSC's Payload Hazardous Servicing Facility on Aug. 3, beginning a three-month campaign to prepare the one-of-a-kind spacecraft for its trip to Mars.
Technicians bolted on MAVEN's high-gain communications antenna Friday.

They planned to install three of the craft's five attitude-controlling reaction wheels, which needed to be recalibrated, according to Jakosky, who said the wheels used by MAVEN are different than the wheels used by NASA's Kepler telescope, which has suspended science operations due to reaction wheel failures.

Plans called for workers inside the clean room to plug in several of MAVEN's suite of scientific instruments undergoing last-minute touch-ups at Space Sciences Laboratory at the University of California at Berkeley.

The first power-up of the MAVEN spacecraft since its arrival in Florida is scheduled for next week.

"Then we'll start checking all the systems out to make sure the flight, and the transportation, there was no issue," Mitchell said. "I'm sure there won't be an issue, but we have to check it. Then we'll go into some deployment testing of some of the appendages, do a dry spin balance of the spacecraft to get the mass properties with everything on-board, fuel the spacecraft with hydrazine, and then pretty soon we'll be getting into integrated operations with the launch vehicle."

With its propellant tank empty, MAVEN weighs less than a ton. With a tank full of hydrazine, MAVEN will tip the scales at more than 5,400 pounds at the time of launch. Most of the propellant will be consumed during a lengthy rocket firing to brake MAVEN into orbit around Mars in September 2014.

MAVEN will be encapsulated inside the two halves of the Atlas 5's four-meter diameter payload fairing around the end of October, then the spacecraft will be trucked to the seaside launch pad in early November, Mitchell said.

With MAVEN perched atop it, the Atlas 5 will roll to the launch pad Nov. 17, ahead of its planned liftoff one day later to begin a 10-month journey to Mars.

If MAVEN blasts off Nov. 18, its arrival is appointed for Sept. 22, 2014, Mitchell said. MAVEN will enter an elongated, oval-shaped orbit and then spiral down to a science orbit with a high point of more than 3,700 miles and a low point 90 miles above the Martian surface.

Controllers will deploy instrument booms and a sensor platform soon after MAVEN's arrival at Mars. The payloads will monitor the solar wind's impact on Mars and scoop up and study gases in the outermost layers of the Martian atmosphere.

"After we get to Mars, there's about a five-week commissioning phase, then we go into one year of operations," Mitchell said.

NASA could extend MAVEN's mission beyond late 2015 if the spacecraft remains healthy and producing good science results. The probe carries enough propellant to stay operational for nearly a decade, according to fuel projections by Lockheed Martin.

"What we're really getting at is understanding the history of the climate, the history of the volatile inventory, and I think the understanding of the history of the habitability of Mars by microbes," Jakosky said. "I see it as a geology mission, or an astrobiology mission, because that's what we're getting at by studying the top of the atmosphere and its interactions with the sun."

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